1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly to an LCD device that prevents formation of bubbles at an display screen area where an image is displayed, and to a method of fabricating an LCD device that controls formation of bubbles which is generated during a process of forming liquid crystal.
2. Description of the Related Art
In general, an LCD device controls light transmissivity of liquid crystal material by application of an electric field in order to display images. Accordingly, the LCD device includes a liquid crystal display panel having liquid crystal cells arranged in a matrix configuration and a drive circuit in order to drive the liquid crystal display panel. The liquid crystal display panel includes pixel electrodes to induce an electric field to each of the liquid crystal cells and a reference electrode, which is commonly called a common electrode. The pixel electrodes are formed on a lower substrate corresponding to the liquid crystal cells, and the common electrode is formed along an entire surface of an upper substrate. In addition, each of the pixel electrodes are connected to a thin film transistor (TFT), which is used as a switching device. Accordingly, the pixel electrodes together with the common electrode drive the liquid crystal cell in accordance with data signals supplied through the TFT.
FIG. 1 is a perspective view of an LCD panel according to the related art. In FIG. 1, an LCD panel includes an upper array substrate 10 and a lower array substrate 20 which are bonded together with a liquid crystal material 8 therebetween. The liquid crystal material 8 includes molecules that rotate in response to an applied electric field, thereby controlling an amount of transmitted light that is incident through the lower array substrate 20.
In FIG. 1, the upper array substrate 10 includes a color filter 4, a common electrode 6, and an upper alignment film (not shown) that are formed on the rear surface of an upper substrate 1. The color filter 4 includes red R, green G, and blue B color filters and allows light of a specific wavelength range to be transmitted, thereby displaying images having specific colors. In addition, a black matrix 2 is formed between color filters 4 of adjacent colors in order to absorb the light that is incident from the adjacent cell, thereby preventing its contrast from deteriorating.
The lower array substrate 20 has a plurality of gate lines 12 and data lines 18 that are formed along an entire surface of the lower substrate 21 to cross each other, and are insulated from each other with a gate insulating film therebetween. In addition, a TFT 16 is formed at each of the intersection areas of the gate and data lines 12 and 18.
The TFT 16 includes a gate electrode connected to the gate line 12, a source electrode connected to the data line 18, and a drain electrode corresponding to the source electrode with a channel part therebetween, wherein the channel part includes an active layer and an ohmic contact layer. In addition, the TFT 16 is connected to the pixel electrode 14 through a contact hole which penetrates a passivation film (not shown). The TFT 16 selectively supplies a data signal transmitted along the data line 18 to the pixel electrode 14 in response to a gate signal transmitted along the gate line 12.
The pixel electrode 14 is located at a cell area that is divided by the gate and data lines 12 and 18, and is formed of a transparent conductive material having high light transmissivity. Accordingly, a potential difference is generated between the pixel electrode 14 and the common electrode 6 by the data signal supplied through the drain electrode. The potential difference generated between the pixel electrode 14 and the common electrode 6 causes the molecules of the liquid crystal material 8 located between the lower substrate 21 and the upper substrate 1 to rotate due to a dielectric anisotropy of the liquid crystal material 8. Accordingly, the light supplied from a light source through the pixel electrode 14 is transmitted toward the upper substrate 1.
Although not shown, the upper array substrate 10 and the lower array substrate 20 sustain a cell gap by a pattern spacer. In addition, the liquid crystal material 8 is injected into an inner space provided by the pattern spacer between the upper and lower array substrates 10 and 20.
A fabricating process for the LCD panel is divided into individual processes of substrate cleaning, substrate patterning, alignment film forming/rubbing, substrate bonding/liquid crystal injection, mounting, inspection, and repair. During the substrate bonding/liquid crystal injection process, the upper array substrate 10 and the lower array substrate 20 are bonded together by use of a sealant (not shown), the liquid crystal material 8 is injected through a liquid crystal injection hole (not shown), and then the liquid crystal injection hole is sealed.
During the liquid crystal injection process, the liquid crystal material 8 and the spacer (not shown) are injected after the sealant is patterned while bonding the upper array substrate 10 and the lower array substrate 20 together. However, bubbles are inevitably generated during the process of injecting the liquid crystal material 8 and the spacer (not shown) into the space which is formed between the upper and lower array substrates 10 and 20, within a vacuum chamber (not shown). Accordingly, defects are generated in the LCD panel due to the formation of the bubbles in the LCD panel. In other words, the bubbles remaining behind on an display screen area where images are displayed should be removed by controlling the liquid crystal injection process.